组织追踪法定量评价急性心肌梗死左心室局部收缩功能的实验研究

目的　探讨组织追踪(tissue tracking ,TT)法定量评价犬急性心肌梗死(AMI)左心室局部收缩功能变化的可行性,为TT法应用于临床诊断急性心肌缺血提供实验依据。方法　选用9条健康杂种犬,于左侧第5肋间开胸,在第一对角支起点以下套扎冠状动脉左前降支(LAD)主干,建立AMI模型。分别于LAD结扎前和结扎后 15、30、60和 120 min,用 TT法在心尖四腔观、心尖二腔观和心尖左室长轴观测量左室收缩期 6 个壁 18个节段心肌的纵向最大位移,心肌缺血区通过心肌染色病理切片确定。结果　9条犬中8条犬成功建立 AMI模型。LAD结扎前,左室收缩期基底至心尖不同节段心肌位移曲线呈波形同步向上梯度样减低的正向波群,基底段与中段和中段与心尖段之间比较心肌位移差异有非常显著性意义(P<0.01)。LAD结扎即刻至 120 min,左室前壁和前间隔缺血节段失去结扎前心肌位移变化的规律性。结扎 LAD 15 min,左室前壁、前间隔最大位移明显减低,30 min后略有恢复趋势,但仍处于低水平。不同时间缺血区节段心肌位移测值与结扎前比较差异有非常显著性意义(P<0.01)。结论　TT能够直观定量评价左室收缩期所有心肌从心底至心尖方向的纵向位移,客观追踪观察AMI左室局部收缩功能的变化,方法简便可靠,可作为一种临床诊断急性心肌缺血的超声定量方法

Quantitative assessment of regional left ventricular contractile function during acute myocardial infarction using tissue tracking echocardiography:an experimental study

Objective To investigate the feasibility of quantitative evaluation for regional left ventricular contractile function during acute myocardial infarction(AMI) using tissue tracking(TT) echocardiography.Methods Nine open-chest mongrel healthy dogs were scanned from the apical four-chamber,two-chamber and long axis views before,and at 15 min,30 min,60 min and 120 min after left anterior decending coronary artery(LAD) ligation.The maximal longitudinal myocardial tracking values(displacements)of 18 segments of left ventricle from these views were measured by TT curves during offline quantitative analysis.The extent of ischemic myocardium was determined by dye-stained specimens.Results AMI modes of 8 dogs were successfully established from 9 dogs.Along the long-axis plane,all maximal longitudinal myocardial displacements decreased significantly from the basal segments to the middle and apical segments(P< 0.01),while no significant differences were found between the walls at baseline.As compared with the data of the baseline,the basal-apical gradient of myocardial displacements was no longer evident in the acute myocardial ischemia situation.The maximal longitudinal myocardial displacements of the infarct walls decreased significantly after 15 min of coronary artery ligation and increased slightly after 30 min,but they were different from the baseline ones and there were significant differences between the two groups(P< 0.01).Conclusions TT may be a promising new tool for the quantification of ischemia-induced regional myocardial dysfunction.